Vertebroplasty increases compression of adjacent IVDs and vertebrae in osteoporotic spines

Teriparatide alone versus vertebroplasty on pain control and radiographic outcomes after osteoporotic vertebral compression fracture

PURPOSE

To investigate efficacy of 3-month teriparatide(TPD) and compare this treatment with vertebroplasty in terms of clinical and radiographic outcomes after osteoporotic vertebral compression fractures (OVCFs).

METHODS

This is a retrospective matched cohort study. Patients who received conservative treatment with at least 3-month TPD treatment for acute OVCF with at least 6 months follow-up were included. Each enrolled TPD case was matched with 2 vertebroplasty cases using age and gender. 30 TPD cases and 60 vertebroplasty cases were enrolled. Patient-reported pain scores were obtained at diagnosis and 1, 3, 6 months after diagnosis. Radiographic parameters including middle body height, posterior body height, wedge angle and kyphotic angle were measured at diagnosis and 6 months after diagnosis. Fracture non-union and subsequent vertebral fracture were evaluated.

RESULTS

TPD treatment showed inferior pain relief to vertebroplasty group at 1 month, but did not show difference at 3 and 6 months after diagnosis. In TPD cases, progression of vertebral body collapse was noted in terms of middle body height and wedge angle at final follow up. Instead, both middle body height and wedge angle increased significantly after operation in the vertebroplasty group. Fracture non-union was confirmed via MRI and 4 TPD patients were diagnosed with non-union (4/30, 13.3%). Subsequent compression fracture within 6 months was significant higher in vertebroplasty group (12/60, 20%) than in TPD group (1/30, 3.3%).

CONCLUSION

In acute OVCFs, 3-month TPD treatment alone showed comparable pain improvement and less subsequent spine fracture than vertebroplasty.

The Closer Vicinity to Treated Vertebrae in Percutaneous Vertebroplasty, the Higher Rate of New Vertebral Compression Fractures at Follow-up

OBJECTIVE

To investigate whether risk of new vertebral compression fractures (NVCFs) was associated with vicinity to treated vertebrae in percutaneous vertebroplasty (PVP) for osteoporotic vertebral compression fractures (OVCFs).

METHODS

All OVCF (T6-L5) patients treated with PVP between January 2016 and December 2020 were retrospectively reviewed. Vicinity to treated vertebrae was defined as the number of vertebrae between an untreated and its closest treated level. The closest treated level was chosen as reference vertebra. Clinical, radiologic, and surgical parameters were compared between groups of reference vertebrae for each vicinity NVCF.

RESULTS

In total, 1348 patients with 1592 fractured and 14,584 normal vertebrae were enrolled. NVCF was identified in 20.1% (271 of 1348) patients in 2.2% (319 of 14584) vertebrae in a mean follow-up time of 24.3 ± 11.9 months. Rate of NVCF in vicinity 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11 level were 4.6% (130 of 2808), 2.4% (62 of 2558), 1.8% (42 of 2365), 1.5% (31 of 2131), 1.3% (23 of 1739), 1.3% (17 of 1298), 0.8% (7 of 847), 0.9% (4 of 450), 0.8% (2 of 245), 0.9% (1 of 117), and 0% (0 of 26), respectively. Rate of NVCF in vicinity 1 level was significantly higher than that in vicinity 2, 3, 4, 5, 6, 7, 8, and 9 level, respectively. However, compared to reference vertebrae for vicinity 1 NVCF, any clinical, radiologic, or surgical parameters were not significantly different in those for vicinity 2, 3, and 4 NVCF, respectively.

CONCLUSIONS

The closer vicinity to treated vertebrae in PVP, the higher rate of NVCF at follow-up. However, any clinical, radiologic, or surgical parameters might not matter in this phenomenon of vicinity-related NVCF.

Static study and numerical simulation of the influence of cement distribution in the upper and lower adjacent vertebrae on sandwich vertebrae in osteoporotic patients: Finite element analysis

Objective

We analyzed the influence of the location of the upper and lower cement on the sandwich vertebrae (SV) by computer finite element analysis.

Materials and Methods

A finite element model of the spinal segment of T11-L1 was constructed and 6 mL of cement was built into T11 and L1 simultaneously. According to the various distributions of bone cement at T11 and L1, the following four groups were formed: (i) Group B-B: bilateral bone cement reinforcement in both T11 and L1 vertebral bodies; (ii) Group L-B: left unilateral reinforcement in T11 and bilateral reinforcement in L1; (iii) Group L-R: unilateral cement reinforcement in both T11 and L1 (cross); (iv) Group L-L: unilateral cement reinforcement in both T11 and L1 (ipsilateral side). The maximum von Mises stress (VMS) and maximum displacement of the SV and intervertebral discs were compared and analyzed.

Results

The maximum VMS of T12 was in the order of size: group B-B < L-B < L-R < L-L. Group B-B showed the lowest maximum VMS values for T12: 19.13, 18.86, 25.17, 25.01, 19.24, and 20.08 MPa in six directions of load flexion, extension, left and right lateral bending, and left and right rotation, respectively, while group L-L was the largest VMS in each group, with the maximum VMS in six directions of 21.55, 21.54, 30.17, 28.33, 19.88, and 25.27 MPa, respectively.

Conclusion

Compared with the uneven distribution of bone cement in the upper and lower adjacent vertebrae (ULAV), the uniform distribution of bone cement in the ULAV reduced and uniformed the stress load on the SV and intervertebral disc. Theoretically, it can lead to the lowest incidence of sandwich vertebral fracture and the slowest rate of intervertebral disc degeneration.

Analysis of adjacent vertebral fracture after percutaneous vertebroplasty: do radiological or surgical features matter?

PURPOSE

To report the incidence and risk factors of adjacent vertebral fracture (AVF) after percutaneous vertebroplasty (PVP) in patients with osteoporotic vertebral compression fractures (OVCFs). We focused to investigate effect of radiological or surgical features on AVF.

METHODS

All patients with OVCFs who were treated with PVP between January 2016 and December 2019 were retrospectively reviewed. Patients were followed up at least 12 months after procedure according to treatment protocol. AVF was defined as postoperatively recurrent intractable back pain and subsequently presence of fracture on magnetic resonance imaging (MRI) in adjacent levels. Clinical, radiological, and surgical factors potentially affecting occurrence of AVF were recorded and analyzed using univariate and multivariate analysis.

RESULTS

Totally, 1077 patients with 1077 fractured vertebrae who underwent PVP were enrolled in the study, after inclusion and exclusion criteria were met. Mean follow-up time was 24.3 ± 11.9 months (range, 12-59 months). AVF was identified in 98 (9.1%) patients. Univariate analysis showed that seven significant factors related to AVF were older age, non-traumatic fracture, cortical disruption on anterior wall, cortical disruption on lateral wall, basivertebral foramen, type-B leakage and type-C leakage. In multivariate analysis, two clinical factors, older age (P = 0.031) and non-traumatic fracture (P = 0.002), were significantly associated with AVF. However, any radiological or surgical factor did not reach significance in final model analysis.

CONCLUSIONS

Incidence of AVF after PVP in patients with OVCFs was 9.1% (98/1077). Older age and non-traumatic fracture were two clinical risk factors for AVF. Neither radiological nor surgical feature was significantly correlated with AVF.

Risk assessment for sandwich vertebral fractures in the treatment of osteoporosis vertebral compression fractures using two methods of bone cement reinforcement

PURPOSE

Bone cement augmentation surgery includes percutaneous vertebroplasty (PVP) and percutaneous kyphoplasty (PKP). In this study, we aimed to investigate the risk of sandwich vertebral fractures in the treatment of osteoporotic vertebral compression fractures via PVP and PKP.

METHODS

We performed a retrospective analytical study and included 61 patients with osteoporotic vertebral compression fractures who underwent PVP and PKP at the Spinal Surgery Department of The Second Hospital of Liaocheng Affiliated with Shandong First Medical University from January 2019 to January 2022. These patients were divided into the following two groups by simple random sampling: group A (N = 30) underwent PVP treatment and group B (N = 31) underwent PKP treatment. The surgical time, fluoroscopy frequency, visual analog scale (VAS) score, amount of bone cement, the leakage rate of bone cement in intervertebral space, Cobb angle, and the incidence of fractures in both groups of sandwich vertebral were recorded after 1 year of follow-up.

RESULTS

No statistically significant difference was found in terms of surgical time, fluoroscopy frequency, and VAS score between the two groups (P > 0.05). However, a statistically significant difference was found in terms of the amount of bone cement, the leakage rate of bone cement intervertebral space, Cobb angle, and the incidence of vertebral body fractures in both groups (P < 0.05). The amount of bone cement, the leakage rate of bone cement in intervertebral space, Cobb angle, and sandwich vertebral fractures were higher in Group A than in Group B.

CONCLUSIONS

When PVP and PKP were performed to treat osteoporotic vertebral compression fractures, the sandwich vertebral exhibited a risk of fracture. PVP exhibited a greater relative risk than PKP, which may be due to the relatively larger amount of bone cement, higher rate of bone cement leakage in the intervertebral space, and larger Cobb angle.

Venous injection of a triphasic calcium-based implant in a sheep model of pulmonary embolism demonstrates minimal acute systemic effects

PURPOSE

Implant leakage is the most common complication of vertebral augmentation. Alternative injectable materials must demonstrate intravascular safety comparable to or better than polymethyl methacrylate (PMMA). This study assessed the systemic effects of a triphasic calcium-based implant or PMMA injected directly into the femoral vein in a large animal model designed to mimic severe intravascular implant leakage.

METHODS

Six skeletally mature female sheep were randomly assigned (n = 3) to either the PMMA or the triphasic implant (AGN1, composition: calcium sulfate, β-tricalcium phosphate, brushite) treatment group. Femoral veins of each sheep were directly injected with 0.5 mL of implant material to mimic leakage volumes reported during PMMA vertebroplasty. To compare acute systemic effects of the materials, cardiovascular parameters, laboratory coagulation markers, and calcium and sulfate serum levels were monitored for 60 min after implant injection. Thrombotic and embolic events were evaluated by radiologic imaging, necropsy, and histopathology.

RESULTS

Heart rate, systemic arterial blood pressure, arterial oxygenation, arterial carbon dioxide content, and coagulation markers remained within physiological range after either AGN1 or PMMA injection. No blood flow interruption in the larger pulmonary vessels was observed in either group. Lung histopathology revealed that the severity of thrombotic changes after AGN1 injection was minimal to slight, while changes after PMMA injection were minimal to massive.

CONCLUSION

Acute systemic effects of intravascular AGN1 appeared to be comparable to or less than that of intravascular PMMA. Furthermore, in this preliminary study, the severity and incidence of pulmonary histological changes were lower for AGN1 compared to PMMA.

Biomechanical comparison between unilateral and bilateral percutaneous vertebroplasty for osteoporotic vertebral compression fractures: A finite element analysis

Background and objective: The osteoporotic vertebral compression fracture (OVCF) has an incidence of 7.8/1000 person-years at 55–65 years. At 75 years or older, the incidence increases to 19.6/1000 person-years in females and 5.2–9.3/1000 person-years in males. To solve this problem, percutaneous vertebroplasty (PVP) was developed in recent years and has been widely used in clinical practice to treat OVCF. Are the clinical effects of unilateral percutaneous vertebroplasty (UPVP) and bilateral percutaneous vertebroplasty (BPVP) the same? The purpose of this study was to compare biomechanical differences between UPVP and BPVP using finite element analysis.

Materials and methods: The heterogeneous assignment finite element (FE) model of T11-L1 was constructed and validated. A compression fracture of the vertebral body was performed at T12. UPVP and BPVP were simulated by the difference in the distribution of bone cement in T12. Stress distributions and maximum von Mises stresses of vertebrae and intervertebral discs were compared. The rate of change of maximum displacement between UPVP and BPVP was evaluated.

Results: There were no obvious high-stress concentration regions on the anterior and middle columns of the T12 vertebral body in BPVP. Compared with UPVP, the maximum stress on T11 in BPVP was lower under left/right lateral bending, and the maximum stress on L1 was lower under all loading conditions. For the T12-L1 intervertebral disc, the maximum stress of BPVP was less than that of UPVP. The maximum displacement of T12 after BPVP was less than that after UPVP under the six loading conditions.

Conclusion: BPVP could balance the stress of the vertebral body, reduce the maximum stress of the intervertebral disc, and offer advantages in terms of stability compared with UPVP. In summary, BPVP could reduce the incidence of postoperative complications and provide promising clinical effects for patients.

Early Percutaneous Vertebroplasty Improves Bone-Cement Integration and Reduces Adjacent Fractures

BACKGROUND

Percutaneous vertebroplasty (PVP) is widely used for treatment of osteoporotic vertebral compression fractures (VCFs). However, the influence of PVP timing (early vs. late) on development of adjacent vertebral fractures has rarely been discussed. This retrospective cohort study aimed to evaluate bone-cement binding for thoracolumbar fractures (T8-L3) using a new assessment method to predict risk for adjacent vertebral fractures.

METHODS

Patients with a single-level T-score ≤ -1.0 of lumbar bone mineral density and a primary osteoporotic VCF in the thoracolumbar region (T8-L3) who underwent PVP from October 2016 to February 2018 at our medical university-affiliated hospital were included. Patients were divided into refracture and non-refracture groups. All patients underwent computed tomography after vertebroplasty. Bone-cement distribution patterns were evaluated using standardized axial computed tomography images of each cemented vertebra by 4 independent observers with ImageJ software. The smoothness index was calculated as a percentage of smooth margins.

RESULTS

Of 51 VCFs, 15 (29.4%) and 36 (70.6%) were refracture and non-refracture VCFs, respectively. The mean smoothness index (MSI) was higher in the refracture group than in the non-refracture group (P < 0.01), with an increased refracture risk that corresponded to increased MSI values (P = 0.004). Spearman correlation coefficient (0.375) showed a positive correlation between the fracture-vertebroplasty interval and MSI (P = 0.01).

CONCLUSIONS

Axial computed tomography images were used to characterize bone-cement binding properties. Patients who underwent early PVP had a lower MSI, better bone-cement integration, and fewer adjacent fractures.

How the clinical dosage of bone cement biomechanically affects adjacent vertebrae

Objective

This study evaluated the biomechanical changes in the adjacent vertebrae under a physiological load (500 N) when the clinically relevant amount of bone cement was injected into fractured cadaver vertebral bodies.

Methods

The embalmed cadaver thoracolumbar specimens in which each vertebral body (T12–L2) had a BMD of < 0.75 g/cm² were used for the experiment. For establishing a fracture model, the upper one third of the L1 vertebra was performed wedge osteotomy and the superior endplate was kept complete. Stiffness of specimens was measured in different states. Strain of the adjacent vertebral body and intervertebral disc were measured in pre-fracture, post-fracture, and after augmentation by non-contact optical strain measurement system.

Results

The average amount of bone cement was 4.4 ml (3.8–5.0 ml). The stiffness of after augmentation was significantly higher than the stiffness of post-fracture (p < 0.05), but still lower than pre-fracture stiffness (p < 0.05). After augmentation, the adjacent upper vertebral strain showed no significant difference (p > 0.05) with pre-fracture, while the strain of adjacent lower vertebral body was significantly higher than that before fracture (p < 0.05). In flexion, T12/L1 intervertebral disc strain was significantly greater after augmentation than after the fracture (p < 0.05), but there was no significant difference from that before the fracture (p > 0.05); L1/2 vertebral strain after augmentation was significantly less than that after the fracture (p < 0.05), but there was no significant difference from that before the fracture (p > 0.05).

Conclusions

PVP may therefore have partially reversed the abnormal strain state of adjacent vertebral bodies which was caused by fracture.

Vertebral collapse and polymethylmethacrylate breakage after vertebroplasty: A case report

RATIONALE

Vertebral augmentation has become the main treatment for osteoporotic vertebral fractures (VFs). In this article, we report a very rare case of vertebral collapse and polymethylmethacrylate (PMMA) breakage after vertebroplasty. We describe the clinical characteristics and revision surgery performed to remove the broken PMMA cement, maintain stability, and corrects the kyphotic deformity, and we analyze the possible causes.

PATIENT CONCERNS

A 72-year-old man who suffered back pain underwent first lumbar vertebra (L1) percutaneous vertebroplasty (PVP) due to osteoporosis and a vertebral fracture in May 2013. Postoperatively, the patient's back pain was markedly alleviated. Unfortunately, his lumbar back pain recurred in November 2015.

DIAGNOSES

Plain radiographs showed collapse of the L1 vertebral body, breakage of the PMMA cement, and severe kyphosis at the thoracolumbar junction.

INTERVENTIONS

The posterior pedicle was internally fixed and an anterior artificial vertebral body implant was placed to maintain stability and correct the kyphotic deformity in a 2-step surgical procedure.

OUTCOMES

The back pain was alleviated and the patient returned to daily life for more than two years.

LESSONS

This case demonstrates that PVP is not a simple minimally invasive surgery, and significant postsurgical care is necessary. The true cause of this rare phenomenon remains unclear, but the long-term use of steroids, new injuries, and poorly corrected kyphosis after PVP may play a role. Surgeons must be aware of the kinds of complications that may occur, including rare complications such as vertebral lysis.

The biomechanical influence of anterior vertebral body osteophytes on the lumbar spine: A finite element study

BACKGROUND CONTEXT

Anterior vertebral body osteophytes are common with degeneration but their biomechanical influence on the whole lumbar spine remains unclear.

PURPOSE

To investigate the biomechanical influence of anterior vertebral body osteophytes on the whole lumbar spine.

STUDY DESIGN/SETTING

This is a study using finite element analysis.

OUTCOME MEASURES

Intersegmental rotation, maximum Mises stress, and intradiscal pressure on the intervertebral discs of different lumbar levels were calculated.

METHODS

A finite element model of an intact lumbar spine was constructed and validated against in vitro studies. The modified models, which had different degrees of anterior vertebral body osteophyte formation (OF) in combination with disc space narrowing, were applied with physiological loadings.

RESULTS

The lumbar levels with various degrees of OF altered the kinematics of these levels, which also affected the whole lumbar spine. In flexion and lateral bending, the segment that was one level inferior to the vertebra with OF showed a trend towards increased range of motion. On the intervertebral discs that were one level inferior to the OF level, a trend towards increase in the maximum von Mises stress was found on the annulus.

CONCLUSIONS

Segments adjacent to levels with anterior vertebral body osteophytes showed increased intersegmental rotation and maximum stress. Further clinical observation should be performed to verify the results in vivo.

Vertebral Fragility Fractures (VFF)-Who, when and how to operate

Vertebral Fragility Fractures (VFF) are common and lead to pain, long term disability and increased mortality. Most patients will have mild to moderate pain symptoms and can be managed conservatively. However, patients with severe pain who have minimal or no pain relief with potent analgesia, or who only achieve adequate pain relief with high doses of morphine based analgesia which results in significant adverse events, should be considered for vertebral augmentation. Ideally, for vertebral augmentation, patients should present within four months of the fracture (onset of acute pain) and have at least 3 weeks of failure of conservative treatment although early intervention may be more appropriate for hospitalised patients, who tend to be older, more frail and likely to be less tolerant to the adverse effects of conservative treatment. The Cardiovascular and Interventional Radiological Society of Europe (CIRSE) recommends Percutaneous Vertebroplasty as the first line surgical augmentation technique for VFF in older people, which has been shown to improve pain symptoms, allow early restoration of functional mobility and may reduce the risk of further vertebral collapse. CIRSE recommends percutaneous Balloon Kyphoplasty as second line treatment in VFF, although the optimal indication is for acute traumatic vertebral fractures (less than 7-10 days) in younger people. Assessment and treatment of underlying osteoporosis is important to reduce the risk of further fractures in older people with VFF.

Comparisons of Anterior Plate Screw Pullout Strength Between Polyurethane Foams and Thoracolumbar Cadaveric Vertebrae

Synthetic polyurethane foams are frequently used in biomechanical testing of spinal medical devices. However, it is unclear what types of foam are most representative of human vertebral trabecular bone behavior, particularly for testing the bone-implant interface. Therefore, a study was conducted to compare polyurethane foam microstructure and screw pullout properties to human vertebrae. Cadaveric thoracolumbar vertebrae underwent microcomputed tomography to assess trabecular bone microstructure. Spine plate screws were implanted into the vertebral body and pullout testing was performed. The same procedure was followed for eight different densities (grades 5-30) of commercially available closed cell (CCF) and open cell foams (OCF). The results indicated that foam microstructural parameters such as volume fraction, strut thickness, strut spacing, and material density rarely matched that of trabecular bone. However, certain foams provided mechanical properties that were comparable to the cadavers tested. Pullout force and work to pullout for screws implanted into CCF grade 5 were similar to osteoporotic female cadavers. In addition, screw pullout forces and work to pullout in CCF grade 8, grade 10, and OCF grade 30 were similar to osteopenic male cadavers. All other OCF and CCF foams possessed pullout properties that were either significantly lower or higher than the cadavers tested. This study elucidated the types and densities of polyurethane foams that can represent screw pullout strength in human vertebral bone. Synthetic bone surrogates used for biomechanical testing should be selected based on bone quantity and quality of patients who may undergo device implantation.

Effect of Bone Cement Volume Fraction on Adjacent Vertebral Fractures After Unilateral Percutaneous Kyphoplasty

STUDY DESIGN

A retrospective study.

SUMMARY OF BACKGROUND DATA

Complications of the bone cement used in vertebroplasty and kyphoplasty procedures have received increasingly more attention, especially for bone cement volume.

OBJECTIVE

The aim of the study was to retrospectively assess the relationship between bone cement volume fraction and adjacent vertebral fracture (AVF) after unilateral percutaneous kyphoplasty (PKP).

MATERIALS AND METHODS

Between 2006 and 2011, 495 patients with single-level osteoporotic vertebral compression fracture (OVCF) were surgically treated by unilateral PKP and had completed 12-month follow-up in our hospital. According to the new OVCF, they were divided into 3 groups: AVF group, non-AVF group, and normal group (who were not new OVCF). On the basis of the value of the plain radiography, the cement volume fraction for the vertebral body was calculated, and cement leakage, bone mineral density, visual analog scale, and Cobb angle of preoperative and postoperative were analyzed.

RESULTS

During the follow-up, 110 (22.2%) patients had new OVCF, and others were normal (n=385). Fifty-two cases were AVF and 58 were non-AVF. The cement volume fraction of AVF group, non-AVF group, and normal group were 32.5%±5.5%, 27.3%±1.8%, and 27.1%±2.6%, respectively. The 95% confidence interval of volume fraction were (31.0, 34.1), (26.8, 27.7), and (26.9, 28.5), respectively. The AVF group showed higher cement volume fraction in 3 groups (P<0.05), and there were no significant difference between non-AVF and normal group (P>0.05). There were 19 (36.5%) patients with cement leakage in AVF group, 12 (20.7%) in non-AVF group, and 68 (17.7%) in normal group. The AVF group showed higher cement leakage (P<0.05). Compared with AVF group and normal group, non-AVF group had lower bone mineral density in preoperation. All groups reported significantly improved visual analog scale scores and Cobb angle on the day of surgery. However, there were no significant difference between the 3 groups.

CONCLUSIONS

Unilateral PKP is an effective and safe procedure for patients with OVCF. However, cement volume should be determined in terms of the vertebral body fraction to obtain a favorable outcome. The risk of AVF and cement leakage will increase obviously with the cement volume fraction increased. We recommend that a bone cement volume fraction of about one fourth is suitable for unilateral PKP.

A single CT-guided percutaneous intraosseous injection of thermosensitive simvastatin/poloxamer 407 hydrogel enhances vertebral bone formation in ovariectomized minipigs

The ultimate goal of osteoporosis treatment is prevention of fragile fracture. Local treatment targeting specific bone may decrease the incidence of osteoporotic fractures. We developed an injectable, thermosensitive simvastatin/poloxamer 407 hydrogel; a single CT-guided percutaneous intraosseous injection augmented vertebrae in ovariectomized minipigs.

INTRODUCTION

The greatest hazard associated with osteoporosis is local fragility fractures. An adjunct, local treatment might be helpful to decrease the incidence of osteoporotic fracture. Studies have found that simvastatin stimulates bone formation, but the skeletal bioavailability of orally administered is low. Directly delivering simvastatin to the specific bone that is prone to fractures may reinforce the target bone and reduce the incidence of fragility fractures.

METHODS

We developed an injectable, thermosensitive simvastatin/poloxamer 407 hydrogel, conducted scanning electron microscopy, rheological, and drug release analyses to evaluate the delivery system; injected it into the lumbar vertebrae of ovariectomized minipigs via minimally invasive CT-guided percutaneous vertebral injection. Three months later, BMD, microstructures, mineral apposition rates, and strength were determined by DXA, micro-CT, histology, and biomechanical test; expression of VEGF, BMP2, and osteocalcin were analyzed by immunohistochemistry and Western blots.

RESULTS

Poloxamer 407 is an effective controlled delivery system for intraosseous-injected simvastatin. A single injection of the simvastatin/poloxamer 407 hydrogel significantly increased BMD, bone microstructure, and strength; the bone volume fraction and trabecular thickness increased nearly 150 %, bone strength almost doubled compared with controls (all P < 0.01); and induced higher expression of VEGF, BMP2, and osteocalcin.

CONCLUSIONS

CT-guided percutaneous vertebral injection of a single simvastatin/poloxamer 407 thermosensitive hydrogel promotes bone formation in ovariectomized minipigs. The underlying mechanism appears to involve the higher expression of VEGF and BMP-2.

Risk factors of adjacent vertebral collapse after percutaneous vertebroplasty for osteoporotic vertebral fracture in postmenopausal women

BACKGROUND

Recently percutaneous vertebroplasty (PVP) was frequently performed for treatment of osteoporotic vertebral fractures (VFs). It is widely accepted that new compression fractures tend to occur adjacent to the vertebral bodies, typically within a month after PVP. To determine the risk factors among several potential predictors for de novo VFs following PVP in patients with osteoporosis.

METHODS

We retrospectively screened the clinical results of 88 patients who had been treated by PVP. Fifteen cases were excluded due to non-union. Of the remaining 73 patients, 19 (26.0%) later returned with pain due to a new vertebral compression fracture. One patient with a non-adjacent fracture and 2 patients with adjacent factures occurring 3 months later were excluded from the study. The 9 male patients were excluded to avoid gender bias. Ultimately, we divided the 61 remaining postmenopausal female patients (mean age: 78.9 years) into the collapse group (14 patients) who had experienced adjacent vertebral collapse after PVP and the non-collapse group (47 patients) who had not. Logistic regression analysis was performed to identify the risk factors for new VFs after PVP.

RESULTS

All 14 cases of adjacent VF occurred within the first month after surgery. The collapse group had significantly advanced age, higher urinary N-terminal cross-linking telopeptide of type I collagen, and lower lumbar and hip bone mineral density (BMD) scores as compared with the non-collapse group. The odds ratios for age, lumbar, total hip, femoral neck, and trochanteric BMD were 4.5, 8.2, 4.5, 7.2, and 9.6, respectively. Positive likelihood ratios suggested that age more than 85 years, lumbar BMD less than 0.700 [-2.6SD], total hip BMD less than 0.700 [-1.8SD], neck BMD less than 0.600 [-2.1], and trochanter BMD less than 0.600 conferred an elevated risk of adjacent VF.

CONCLUSIONS

Our study revealed that advanced age and decreased lumbar and hip BMD scores most strongly indicated a risk of adjacent VF following PVP.

Vertebroplasty increases trabecular microfractures in elderly female cadaver spines

This study assessed whether vertebroplasty increases trabecular bone microfractures in adjacent vertebrae of elderly female cadavers. Results indicated microfractures were almost two times greater in superior adjacent vertebrae for vertebroplasty treated spines compared to non-treated controls. This finding may aid in developing improved treatments for osteoporotic women with vertebral fractures.

INTRODUCTION

Although vertebroplasty may stabilize compression fractures and reduce pain, subsequent vertebral fractures occur in approximately 25 % of patients, reducing the overall safety of this procedure. This is particularly a concern in vertebrae surrounding the treated level where bone cement may cause abnormal transfer of forces to adjacent spinal structures. Therefore, the objective of this study was to quantify the effects of vertebroplasty on local trabecular bone damage in adjacent vertebrae.

METHODS

Five level motion segments (T11-L3) from osteopenic/osteoporotic female cadaver spines (T-score -2.9 ± 1.0) were assigned into either vertebroplasty or control (no vertebroplasty) groups (n = 10/group) such that T-score, trabecular microarchitecture, and age were similar between groups. Compression fractures were created in the L 1 vertebra of all specimens and PMMA bone cement was injected into the fractured vertebra of vertebroplasty specimens. All spine segments were subjected to cyclic axial compression (685-1370 N) for 115,000 cycles. Post-testing, trabecular cubes were cut from adjacent (T12 and L2) vertebral bodies and histologically processed. Trabecular microfractures were identified and normalized by bone area in each section.

RESULTS

There were significantly more trabecular microfractures (p < 0.001) in superior adjacent vertebral bodies of the vertebroplasty group (0.091 ± 0.025 microfractures/mm(2)) when compared to the control group (0.049 ± 0.018 microfractures/mm(2)). However, there was no difference in trabecular microfractures (p = 0.835) between vertebroplasty (0.045 ± 0.022 microfractures/mm(2)) and control groups (0.035 ± 0.013 microfractures/mm(2)) for inferior adjacent vertebral bodies.

CONCLUSIONS

Vertebroplasty specifically impacts the superior adjacent vertebrae of elderly female spines resulting in almost two times more trabecular microfractures when compared to non-treated controls.

Repeated vertebral augmentation for new vertebral compression fractures of postvertebral augmentation patients: a nationwide cohort study

Purpose

Postvertebral augmentation vertebral compression fractures are common; repeated vertebral augmentation is usually performed for prompt pain relief. This study aimed to evaluate the incidence and risk factors of repeat vertebral augmentation.

Methods

We performed a retrospective, nationwide, population-based longitudinal observation study, using the National Health Insurance Research Database (NHIRD) of Taiwan. All patients who received vertebral augmentation for vertebral compression fractures were evaluated. The collected data included patient characteristics (demographics, comorbidities, and medication exposure) and repeat vertebral augmentation. Kaplan–Meier and stratified Cox proportional hazard regressions were performed for analyses.

Results

The overall incidence of repeat vertebral augmentation was 11.3% during the follow-up until 2010. Patients with the following characteristics were at greater risk for repeat vertebral augmentation: female sex (AOR=1.24; 95% confidence interval [CI]: 1.10–2.36), advanced age (AOR=1.60; 95% CI: 1.32–2.08), diabetes mellitus (AOR=4.31; 95% CI: 4.05–5.88), cerebrovascular disease (AOR=4.09; 95% CI: 3.44–5.76), dementia (AOR=1.97; 95% CI: 1.69–2.33), blindness or low vision (AOR=3.72; 95% CI: 2.32–3.95), hypertension (AOR=2.58; 95% CI: 2.35–3.47), and hyperlipidemia (AOR=2.09; 95% CI: 1.67–2.22). Patients taking calcium/vitamin D (AOR=2.98; 95% CI: 1.83–3.93), bisphosphonates (AOR=2.11; 95% CI: 1.26–2.61), or calcitonin (AOR=4.59; 95% CI: 3.40–5.77) were less likely to undergo repeat vertebral augmentation; however, those taking steroids (AOR=7.28; 95% CI: 6.32–8.08), acetaminophen (AOR=3.54; 95% CI: 2.75–4.83), or nonsteroidal anti-inflammatory drugs (NSAIDs) (AOR=6.14; 95% CI: 5.08–7.41) were more likely to undergo repeat vertebral augmentation.

Conclusion

We conclude that the incidence of repeat vertebral augmentation is rather high. An understanding of risk factors predicting repeat vertebral augmentation provides valuable basis to improve health care for geriatric populations.

Effects of vertebroplasty on endplate subsidence in elderly female spines

OBJECT

The aim in this study was to quantify the effects of vertebroplasty on endplate subsidence in treated and adjacent vertebrae and their relationship to endplate thickness and underlying trabecular bone in elderly female spines.

METHODS

Vertebral compression fractures were created in female cadaveric (age range 51-88 years) thoracolumbar spine segments. Specimens were placed into either the control or vertebroplasty group (n = 9/group) such that bone mineral density, trabecular microarchitecture, and age were statistically similar between groups. For the vertebroplasty group, polymethylmethacrylate bone cement was injected into the fractured vertebral body under fluoroscopy. Cyclic compression (685-1370 N sinusoid) was performed on all spine segments for 115,000 cycles. Micro-CT scans were obtained before and after cyclic loading to quantify endplate subsidence. Maximum subsidence was compared between groups in the caudal endplate of the superior adjacent vertebra (SVcau); cranial (TVcra) and caudal (TVcau) endplates of the treated vertebra; and the cranial endplate of the inferior adjacent vertebra (IVcra). In addition, micro-CT images were used to quantify average endplate thickness and trabecular bone volume fraction. These parameters were then correlated with maximum endplate subsidence for each endplate.

RESULTS

The maximum subsidence in SVcau endplate for the vertebroplasty group (0.34 ± 0.58 mm) was significantly (p < 0.05) greater than for the control group (-0.13 ± 0.27 mm). Maximum subsidence in the TVcra, TVcau, and IVcra endplates were greater in the vertebroplasty group, but these differences were not significant (p > 0.16). Increased subsidence in the vertebroplasty group manifested locally in the anterior region of the SVcau endplate and in the posterior region of the TVcra and TVcau endplates (p < 0.10). Increased subsidence was observed in thinner endplates with lower trabecular bone volume fraction for both vertebroplasty and control groups (R(2) correlation up to 62%). In the SVcau endplate specifically, these 2 covariates aided in understanding subsidence differences between vertebroplasty and control groups.

CONCLUSIONS

Bone cement injected during vertebroplasty alters local biomechanics in elderly female spines, resulting in increased endplate disruption in treated and superior adjacent vertebrae. More specifically, bone cement increases subsidence in the posterior regions of the treated endplates and the anterior region of the superior caudal endplate. This increased subsidence may be the initial mechanism leading to subsequent compression fractures after vertebroplasty, particularly in vertebrae superior to the treated level.